Well creatures know conditions on them but they should not know what class abilities you have.
E.g., I mark a Kobold as a fighter. It shifts and I smack it (it should not know about combat challenge). Next round my ranger/fighter multiclass buddy decides to mark this Kobold. It should "assume" that this guy is able to smack him if he shifts. The DM should not "know" that the multi-class ranger does not have combat challenge and cannot in fact take that attack if it shifts.
Well, the way the rules are written, the creature knows ALL EFFECTS of any power used on him -- including that if he's marked by you and he shifts, you can whack him. The point is to allow creatures to make intelligent tactical decisions, and not burden the DM with trying to second-guess what the creature knows. Maybe the kobold has faced fighters before and can see by your stance and position that you're going to be able to swing at him no matter how cautiously he moves.
Does it know a fighter's OAs stop movement in that case? If so, how does it determine you're a fighter and not ranger or rogue, or even a paladin?
The point was I wasn't sure I'd include the combat challenge ability as part of the power used to mark something. What if I mark it with some other fighter power? I can still use combat challenge attacks it if its marked by one of those specific marking powers fighters get.
Does it know a fighter's OAs stop movement in that case? If so, how does it determine you're a fighter and not ranger or rogue, or even a paladin?
The point was I wasn't sure I'd include the combat challenge ability as part of the power used to mark something. What if I mark it with some other fighter power? I can still use combat challenge attacks it if its marked by one of those specific marking powers fighters get.
Be careful with your rules interpretation here. The attack provided by the fighter's Mark/Combat Challenge when an enemy shifts/attacks someone else is an immediate reaction, not an OA. Thus, it is limited to only once per round and does NOT stop movement, nor does the fighter receive his Wisdom modifier as a bonus to the attack.